geosphere (version 1.5-1)

span: Span of polygons

Description

Compute the approximate surface span of polygons in longitude and latitude direction. Span is computed by rasterizing the polygons; and precision increases with the number of 'scan lines'. You can either use a fixed number of scan lines for each polygon, or a fixed band-width.

Usage

span(x, ...)

Arguments

x

a SpatialPolygons* object or a 2-column matrix (longitude/latitude)

...

Additional arguments, see Details

Value

• A list, or a matrix if a function fun is specified. Values are in the units of r (default is meter)

Details

The following additional arguments can be passed, to replace default values for this function rll{ nbands Character. Method to determine the number of bands to 'scan' the polygon. Either 'fixed' or 'variable' n Integer >= 1. If nbands='fixed', how many bands should be used res Numeric. If nbands='variable', what should the bandwidth be (in degrees)? fun Logical. A function such as mean or min. Mean computes the average span r Numeric. Radius of the earth; default=6378137m }

Examples

pol <- rbind(c(-180,-20), c(-160,5), c(-60, 0), c(-160,-60), c(-180,-20))
plot(pol)
lines(pol)
# lon and lat span in m
span(pol, fun=max) 
x <- span(pol) 
max(x$latspan)
mean(x$latspan)
plot(x$longitude, x$lonspan)

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